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Amyotrophic lateral sclerosis and smoking: correlation is discovered

The scientists of the Harvard School of Public Health revealed that cigarette smoking may elevate risk to get amyotrophic lateral sclerosis (ALS). This neurodegenerative disease is currently incurable, and its causes still remain unknown in most cases.

To investigate correlation between amyotrophic lateral sclerosis and cigarette smoking the researchers used data from five studies which lasted from 7 to 28 years. They examined information about more than one million people of whom about eight hundred had ALS. The study showed that incidence of ALS increased with age, and was higher in men than women.

Individuals who had ever smoked had elevated risk of developing the disease comparing with those who had never tried to smoke cigarettes. Among smokers the risk of ALS was higher for those who started to smoke earlier.

The risk of the disease was also associated with the pack-years smoked (the quantity of packs per day multiplied by the time of smoking). Besides, the number of cigarettes per day and duration of smoking were correlated with ALS when examined separately. Additional ten cigarettes per day increased risk of the disease by 10 percent, and each ten years of smoking did it by 9 percent.

The researchers suggest that parts of cigarette smoke such as nitric oxide may directly damage nerve cells causing ALS. Moreover, smoking provokes oxidative stress as cigarette smoke contains agents generating free radicals. It is also known that increased risk of ALS is associated with formaldehyde, a product of tobacco burning. The research contributes to further investigation of ALS development.